The present invention relates to a method of operating an electrically erasable programmable read only memory cell which is independent of the programmed condition of the aforesaid cell.
A basic conventional three transistor electrically erasable programmable read only memory device (EEPROM) exhibits variations in access time depending on whether the EEPROM cell way previously programmed or not. In particular an increase in access time occurs due to the time needed to precharge the read line in the case where the floating gate of the EEPROM cell was made positive during a previous programming operation. In the latter case there results a larger capacitance in the "write" line due to the fact that the positive voltage on the floating gate maintains the transistor coupled between the "read" and "write" lines in a conducting state. Since the read line is in common with all EEPROM cells on a given column, the increase in capacitance of the read line becomes very significant when all cells in a column have been programmed such that their floating gates have a positive potential.
Accordingly, it is an object of this invention to provide an improved electrically erasable programmable memory device with a faster access time.
It is a further object of this invention to provide such a memory device whose access time is independent of the programmed state of the device.